Fire department official Chris Margetts said the first dead miner was found at the bottom of the main mine shaft and the second was found where he had been working in the Gleision Colliery near Swansea.
Margetts said there was no sign of the trapped miners where the bodies were found which means they've moved away.
"The search and rescue operation is still on-going and we maintain hope we can find them alive," he said.
Superintendent Phil Davies, of South Wales Police, said the body of a miner found earlier in the day has been recovered and that both families have been informed.
The trapped miners have been named as Phillip Hill, 45, from Neath, Charles Bresnan, 62, David Powell, 50, and Garry Jenkins, 39, all from the Swansea Valley.
"This is a terrible situation getting worse and it just got worse," said local lawmaker Peter Hain. He said one bright sign for those still trapped was that rescue workers had discovered there is oxygen in the vicinity of the mine.
Hain extended his sympathies to the miners' families -- sentiments echoed by Arbishop of Canterbury Rowan Williams, who said he is praying for all involved and that there will be "better news" today.
Prime Minister David Cameron said "every support will be given to the emergency services," adding that later "in due course we must ensure we fully understand and learn from the causes of this accident."
Cameron is being updated regularly on the situation and has been in touch with local police and Hain, according to a spokeswoman for the prime minister.
Authorities have said three other miners managed to get out of the mine after the accident Thursday morning.
One was in the hospital listed as critically ill, while the two others escaped largely unharmed and were aiding in the rescue operation.
Rescue teams are pumping water out of the pit, excavating blockages and shoring up the tunnels. Last night divers trying to reach the men were forced to abandon their attempts.
The mine burrowed into a steep and isolated hillside, is one of the few remainders of Britain's once-mighty mining industry.
South Wales was long synonymous with coal mining, as immortalized by Richard Llewellyn's novel "How Green Was My Valley," whose film version won the 1941 U.S. Academy Award as best picture. Cardiff, Wales' main port city, once led the world in coal exports.
However, Britain's Conservative government under Margaret Thatcher shut down the mines following a yearlong showdown in 1984 with the miners' union. In the year of the strike, there were 196,000 miners working in Britain; now there are about 6,000.
The worst mining accident in British history was in 1913, when 439 miners were killed in a gas explosion at the Senghenydd colliery in South Wales. In a 1966 disaster that shocked the world, an avalanche of coal sludge buried a school in the village of Aberfan, killing 116 children and 28 adults.
Seven people have been killed in mining accidents in Britain since 2006, according to Health and Safety Executive statistics.